This invention relates to a cutting system for cutting slab goods.
Cutting systems utilizing sophisticated computer control have been used to perform intricate cutting operations based on pre-loaded data which controls the direction of movement of a cutting tool. Typical systems have used a carriage which traverses a cutting station in one direction carrying on it a cutting tool which moves in an orthogonal direction to the carriage. By coordinated movements of the cutting tool and carriage, complex shapes may be cut.
This technique of cutting is well documented in the prior art. For example, U.S. Pat. No. 3,978,748, commonly assigned, shows a fluid cutting jet system having coordinated carriage and cutting tool motions. In the context of torch cutting machines, U.S. Pat. No. 2,336,596 is a representative system showing movement of torches in a tracing movement across a cutting table. A sophisticated cutting system utilizing fluid jet techniques is also disclosed in the applicants' application Ser. No. 758,368 and now U.S. Pat. No. 4,140,038. That system has specific applicability to the present invention in terms of fluid handling techniques. Still another prior art technique utilizing precise indexing of sheet material in the system is disclosed in U.S. Pat. No. 3,844,861.
These prior art cutting systems generally share a common trait in that continuous or roll goods are used as the input material for cutting. That is, in the prior art, materials to be cut generally have uniform parallel longitudinal edges. They may be fed across the table and maintained in an accurate registration utilizing a variety of techniques. For example, in the U.S. Pat. No. 3,844,861, the roll goods are continuously fed off of a storage or supply spool and are pulled across the cutting surface by means of the carriage. Since the carriage is under computer control and its drive system determines accurately the position of the carriage vis-a-vis the cutting table, accurate registration of materials in the cutting area can be attained. Moreover, in a variance of the basic technique disclosed in the U.S. Pat. No. 3,844,861, registration can further be enhanced by having a series of sprocket holes disposed on the longitudinal peripheral edges of the material to be cut or otherwise worked upon.
In the case of techniques utilizing flame cutters, similar registration is maintained because the work piece has parallel longitudinal edges and is either of a known rectangular shape or fed continuously from a supply having uniform work blanks. Typical are the systems disclosed in U.S. Pat. Nos. 3,866,892 and 2,345,314.
A variation is shown in the commonly-assigned U.S. Pat. No. 3,978,748. That patent shows the technique of handling continuous or roll goods across the cutting table by means of a feed belt at the input side of the cutting station. U.S. Pat. No. 3,978,748 also shows the use of trays for loading of materials into the cutting area. U.S. Pat. No. 3,978,748, however, is silent concerning problems of material registration and measurement as a precursor to a precision cutting operation.
This invention is directed to the problems associated with the handling and cutting of slab goods. These goods, such as hides, synthetic shoe bottom materials and the like, are generally of random size. In the case of slab goods, the individual sheets are generally not formed as rectangles or other regular blank sizes. The slab goods are generally received for cutting with only rough edge treatment such that no uniformity between various sheets is present. Accordingly, the usable area will vary between individual sheets of slab goods.
In order to productively cut these materials with a maximum utilization of material, a system must take into account the maximum usable area on each slab so that in the production of a marker, material usage will be maximized.
Moreover, multiple plies of slabs will generally be cut at the same time so that, when overlying each other, the same cut will generate a multiple number of parts. In the case of cutting multiple plies, added system capability is mandated to generate the maximum usable area for the slab stack. Then, a cutting marker is produced which will provide maximum material utilization over the range in dimensions of each of the slabs.
The technique for marker making in the context of computer operations is disclosed in commonly-assigned U.S. Pat. No. 3,887,903. That patent discloses a technique for generating an apparel pattern marker utilizing interactive computer techniques.
In treating slab goods, prior art cutting techniques have been limited to separate measurements which are then fed to an off-line computer station for generating a marker compatible with that individual slab. Techniques of simultaneous cutting of multiple slabs have not generally been efficient in maximizing raw materials or throughput. Alternatively, the prior art has not used computerized marker techniques with slab goods but utilizes die cutting and the like to attempt maximum slab utilization. In the context of systems which cut, for example, a shoe sole, reduction of waste material is of crucial importance. The cost of such materials, for example, leather hides or composite shoe sole bottoms, makes it mandatory that efficiency of materials is maintained to a maximum. Hence, computerized techniques for generating markers and grading for sizes have attained commercial significance in such raw materials. However, the use of such a marker for multiple slabs or real time operation has been the subject of continuing research.
A proposed system using an off-line marker maker is disclosed in "Automation in Cutting Shoe Components," Volume 24, British Boot and Shoe Institution, May/June 1978. That system, using a die cutter, employs sections for measurement, cut and off-load. Measurements of a single slab are made and manually entered into an off-line marker maker. The marker is generated while the knife is loaded, and the single ply is then cut. The system does not measure multiple plies, and the marker maker is not suitable for multiple ply optimization. Moreover, measurements are not automatically transferred to the marker maker. Although throughput is increased, the system is limited to die cutting. Registration of the slabs between the measuring and cutting stations is not considered since an X-Y cutting system is not used. Also, the marker maker is limited to the cutting of a size specified in the die and cannot, on one ply, cut a multitude of different shapes. Hence, the proposed system does not achieve the necessary level of efficiency to make it commercially attractive.
Another problem in prior art techniques utilized in cutting slab goods has been the problem of maintaining adequate throughput in the machine. As previously indicated, one prior art technique is to generate on an off-line basis a separate marker which is then fed into the cutting system as a set of instructions to govern cutting operation. However, system delays while the data is entered and the marker is being generated reduce throughput of the machine. Accordingly, a need exists within this technology to provide a system which has compatible measuring and marker generation compatibility. Stated slightly differently, throughput in the machine can be improved if the marker can be generated on a real time basis following measurements of individual slabs.
Another problem with the prior art in terms of maintaining throughput in a cutting system has been the requirement that the slabs be physically transported from a measuring station which is remote from the cutting station. Hence, at one point in the system, slab area is determined by measurement, and the marker is laid out. The slabs must then be transported to a cutting system, placed on the cutting bed, and once positioned, the cut sequence can then begin. Obviously, delays in cutting are inherent because the system is dependent on individual handling techniques. Inaccuracies also result due to misalignment of the material to be cut on the cutting surface.
Moreover, in devices where belts are used to physically move the slab goods into the cutting area, the problem of accurate registration remains. That is, although the goods are physically measured in one station, unless they can be aligned in the cutting station with precision, the generation of the marker will not correspond to the position of the slab goods vis-a-vis known locations in the cutting area. Hence, for real time throughput, a requirement still exists that the goods once measured be properly moved and aligned in the cutting station such that compatibility of measuring points is maintained.
Yet another problem in the prior art is that of holding down the slab goods as the cutting sequence commences. In the context of roll goods, techniques such as clamping at end points in the cutting area are commonly utilized. Clamping or otherwise holding the materials in the cutting area, for example, by vacuum hold-down techniques, allows the length of continuous roll goods to be held in place while the cut sequence commences. However, in dealing with slab goods, as previously indicated, unequal lengths and widths are commonplace. Hence, the use of stationary clamps is not feasible because, in many cutting operations, the slabs themselves will not reach the fixed position of the clamps at the extreme ends of the cutting table. Hence, a requirement exists that some technique be devised for holding down materials of varying sizes in the cutting area.